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<TITLE>Boolean Vectors</TITLE>
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<H2>5.3 Boolean Vectors</H2>
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<P>In the Standard C++ Library, <B><I><A HREF="../stdlibref/vector.html">vector</A></I></B>s of bit values (boolean 1/0 values) are handled as a special case, so that the values can be efficiently packed with several elements to a word. The operations for a boolean <B><I>vector</I></B>, <B><I>vector&lt;bool&gt;</I></B>, are a superset of those for an ordinary <B><I>vector</I></B>, only the implementation is more efficient.</P>
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<P>One new member function added to the boolean <B><I><A HREF="../stdlibref/vector.html">vector</A></I></B> datatype is <SAMP>flip()</SAMP>. When invoked, this function inverts all the bits of the <B><I>vector</I></B>. Boolean <B><I>vector</I></B>s also return as reference an internal value that also supports the <SAMP>flip()</SAMP> member function:</P>

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std::vector&lt;bool&gt; bvec(27);
bvec.flip();               // flip all values
bvec[17].flip();           // flip bit 17
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<P>The <B><I><A HREF="../stdlibref/vector.html">vector&lt;bool&gt;</A></I></B> also supports an additional <SAMP>swap()</SAMP> member function that allows swapping the values indicated by a pair of references: </P>

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bvec.swap(bvec [17], bvec [16]);
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